In modern society energy is consumed by people and industries, e.g. for producing various products, for transport and production of food. Energy could be produced in several forms and from different energy sources. For instance, electricity is often produced from hydroelectric power plants, combustion of coal, oil, or gas. Traditionally, heat has been produced from local combustion or district heating power plants.
With an increasing population and demands for services, energy consumption strongly increases which negatively affects our environment significantly in a negative way. Combustion produces large amount of carbon dioxide and other greenhouse gases. Hydroelectric power plants require large territories to be drowned, etc.
In order to reduce our footprint and negative impression on our environment, demands have been raised for more clean and environmental friendly energy production. Today, renewable energy is produced from wind, sun, ocean waves, etc. The sun provides large amounts of energy to our planet in form of radiated sun beams. Solar radiation can be used by solar cells to generate electricity, e.g. in form of solar cells, or by solar collectors to generate thermal heat.
A concentrating solar collector uses mirrors, lenses, or combinations thereof, to focus the solar radiation in form of a point or a line. In trough-formed concentrating solar collectors a reflector is formed as a curved elongated mirror, which reflects the solar radiation on a receiver arranged along a focusing line of the reflector. The receiver is commonly a black tube filled with a transport fluid, such as water, glycol, or oil. The tube is heated by the concentrated solar radiation and the heat is transferred to the transport fluid that is circulated in a system where the hot transport fluid could be used. The heated transport fluid may be used both as process heat in industrial processes as in district heating, etc.
With reference to FIG. 1, which is a schematic illustration in a perspective view, an example of a concentrating solar collector 100 will now be described.
The concentrating solar collector 100 is a so called PTC (Parabolic Trough Collector, sometimes alternatively referred to as Parabolic Trough solar Collector) and comprises an elongated trough-formed reflector 102 and a fluid tube 104. The fluid tube 104 is arranged at a focus-line of the reflector 102 and the centre-line of the fluid tube 104 is situated such that it substantially coincides with the focus-line of the reflector 102. Through the fluid-tube 104 a transport liquid, e.g. water, flows from one end to the other end (illustrated by the arrows). The transport fluid is then heated by sunbeams reflected by the reflector 102 when hitting the fluid tube 104.
The fluid tube 104 is held by a holder arrangement 106 that situates the fluid tube 104 at the focus-line.
To improve the amount of heat which could be taken care of in PTC arrangements, various construction parameters of reflectors, e.g. material and dimensions have been elaborated.
An example of a PTC solar collector is disclosed in the patent publication WO2010/047656, A1.
It is a challenge to find solutions for improved efficiency in systems for solar energy production.